PHP Example - AJAX Poll
AJAX Poll
The following example will demonstrate a poll where the result is shown without reloading.
Do you like PHP and AJAX so far?
Example Explained - The HTML Page
When a user chooses an option above, a function called "getVote()" is executed. The function is triggered by the "onclick" event:
<html>
<head>
<script>
function getVote(int)
{
var xmlhttp=new XMLHttpRequest();
xmlhttp.onreadystatechange=function() {
if (this.readyState==4 && this.status==200) {
document.getElementById("poll").innerHTML=this.responseText;
}
}
xmlhttp.open("GET","poll_vote.php?vote="+int,true);
xmlhttp.send();
}
</script>
</head>
<body>
<div id="poll">
<h3>Do you like PHP and AJAX so far?</h3>
<form>
Yes:
<input type="radio" name="vote"
value="0" onclick="getVote(this.value)"><br>
No:
<input type="radio" name="vote"
value="1" onclick="getVote(this.value)">
</form>
</div>
</body>
</html>
The getVote() function does the following:
- Create an XMLHttpRequest object
- Create the function to be executed when the server response is ready
- Send the request off to a file on the server
- Notice that a parameter (vote) is added to the URL (with the value of the yes or no option)
The PHP File
The page on the server called by the JavaScript above is a PHP file called "poll_vote.php":
<?php
$vote = $_REQUEST['vote'];
//get content of textfile
$filename = "poll_result.txt";
$content = file($filename);
//put content in array
$array = explode("||", $content[0]);
$yes = $array[0];
$no = $array[1];
if ($vote == 0) {
$yes = $yes + 1;
}
if ($vote == 1) {
$no = $no + 1;
}
//insert votes to txt file
$insertvote = $yes."||".$no;
$fp = fopen($filename,"w");
fputs($fp,$insertvote);
fclose($fp);
?>
<h2>Result:</h2>
<table>
<tr>
<td>Yes:</td>
<td><img src="poll.gif"
width='<?php echo(100*round($yes/($no+$yes),2)); ?>'
height='20'>
<?php echo(100*round($yes/($no+$yes),2)); ?>%
</td>
</tr>
<tr>
<td>No:</td>
<td><img src="poll.gif"
width='<?php echo(100*round($no/($no+$yes),2)); ?>'
height='20'>
<?php echo(100*round($no/($no+$yes),2)); ?>%
</td>
</tr>
</table>
The value is sent from the JavaScript, and the following happens:
- Get the content of the "poll_result.txt" file
- Put the content of the file in variables and add one to the selected variable
- Write the result to the "poll_result.txt" file
- Output a graphical representation of the poll result
The Text File
The text file (poll_result.txt) is where we store the data from the poll.
It is stored like this:
0||0
The first number represents the "Yes" votes, the second number represents the "No" votes.
Note: Remember to allow your web server to edit the text file. Do NOT give everyone access, just the web server (PHP).
